Method for treating intervertebral discs

ABSTRACT

A device is described that may be positioned at a location in an intervertebral disc for diagnosis or treatment of the disc. Treatment may include, for example, applying energy or removing material, and may decrease intradiscal pressure. Radiofrequency energy may be applied. A percutaneous method of repairing a fissure in the annulus pulposus comprises placing an energy source adjacent to the fissure and providing sufficient energy to the fissure to raise the temperature to at least about 45-70° C. and for a sufficient time to cause the collagen to weld. An intervertebral fissure also can be treated by placing a catheter with a lumen adjacent to the fissure and injecting sealant into the fissure via the catheter, thereby sealing the fissure. An intervertebral fissure additionally can be treated by providing a catheter having a distal end, a proximal end, a longitudinal axis, and an intradiscal section at the catheter&#39;s distal end on which there is at least one functional element. The next step is applying a force longitudinally to the proximal of the catheter which is sufficient to advance the intradiscal section through the nucleus pulposus and around an inner wall of an annulus fibrosus, but which force is insufficient to puncture the annulus fibrosus. Next the functional element is positioned at a selected location of the disc by advancing or retracting the catheter and optionally twisting the proximal end of the catheter. Then the functional unit treats the annular fissure. Optionally, there is an additional step of adding a substance to seal the fissure. An externally guidable intervertebral disc apparatus also is disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 10/388,609, filed Mar. 17, 2003, which is a continuation ofU.S. patent application Ser. No. 09/707,627, filed, Nov. 6, 2000, nowU.S. Pat. No. 6,547,810, which is a continuation of U.S. applicationSer. No. 09/236,816, filed Jan. 25, 1999, now U.S. Pat. No. 6,290,715,which is a continuation of (i) U.S. application Ser. No. 09/162,704filed Sep. 29, 1998, now U.S. Pat. No. 6,099,514, (ii) U.S. patentapplication Ser. No. 09/153,552 filed Sep. 15, 1998, now U.S. Pat. No.6,126,682, and (iii) U.S. patent application Ser. No. 08/881,525, nowU.S. Pat. No. 6,122,549, U.S. patent application Ser. No. 08/881,692,now U.S. Pat. No. 6,073,051, U.S. patent application Ser. No.08/881,527, now U.S. Pat. No. 5,980,504, U.S. patent application Ser.No. 08/881,693, now U.S. Pat. No. 6,007,570, and U.S. patent applicationSer. No. 08/881,694, now U.S. Pat. No. 6,095,149, each filed Jun. 24,1997, claiming priority from provisional application Nos. 60/047,820,60/047,841,60/047,818, and 60/047,848, each filed May 28, 1997,provisional application No. 60/045,941, filed May 8, 1997, andprovisional application Nos. 60/029,734, 60/029,735, 60/029,600, and60/029,602, each filed Oct. 23, 1996. This application is acontinuation-in-part of U.S. patent application Ser. Nos. 09/876,833,09/876,832, and 09/876,831, each filed Jun. 6, 2001. This application isa continuation-in-part of U.S. patent application Ser. No. 10/624,894,filed Jul. 23, 2003, which is a divisional of U.S. patent applicationSer. No. 09/753,786, filed Jan. 2, 2001, now U.S. Pat. No. 6,645,203,which is a continuation-in-part of U.S. patent application Ser. No.09/022,688, filed Feb. 12, 1998, now U.S. Pat. No. 6,168,593, whichclaims priority from provisional application No. 60/037,620, filed Feb.12, 1997. This application is a continuation-in-part of U.S. patentapplication Ser. No. 10/242,777, filed Sep. 13, 2002, which is adivisional of U.S. patent application Ser. No. 09/340,065, filed Jun.25, 1999, now U.S. Pat. No. 6,461,357, which is a continuation-in-partof U.S. patent application Ser. No. 09/022,612, filed Feb. 12, 1998, nowU.S. Pat. No. 6,135,999, which claims priority from provisionalapplication No. 60/037,782, filed Feb. 12, 1997. This application is acontinuation-in-part of U.S. patent application Ser. Nos. 09/776,231 and09/776,186, both filed Feb. 1, 2001, both of which are divisionals ofU.S. patent application Ser. No. 09/272,806, filed Mar. 19, 1999, nowU.S. Pat. No. 6,258,086, which claims priority from provisionalapplication No. 60/078,545, filed Mar. 19, 1998. This application is acontinuation-in-part of U.S. patent application Ser. No. 09/884,859,filed Jun. 18, 2001, which is a continuation of U.S. patent applicationSer. No. 09/792,628, filed Feb. 22, 2001, which claims priority fromprovisional application No. 60/185,221, filed Feb. 25, 2000. Thisapplication is a continuation-in-part of U.S. patent application Ser.No. 09/664,473, filed Sep. 18, 2000, which is a continuation of U.S.patent application Ser. No. 08/696,051, filed Aug. 13, 1996, nowabandoned. All of the above-mentioned applications are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

[0002] This document relates to methods and apparatuses for modifyingintervertebral disc tissue and more particularly to the treatment ofannular fissures and other conditions using percutaneous techniques toavoid major surgical intervention.

BACKGROUND

[0003] Intervertebral disc abnormalities have a high incidence in thepopulation and may result in pain and discomfort if they impinge on orirritate nerves. Disc abnormalities may be the result of trauma,repetitive use, metabolic disorders and the aging process and includesuch disorders but are not limited to degenerative discs (i) localizedtears or fissures in the annulus fibrosus, (ii) localized discherniations with contained or escaped extrusions, and (iii) chronic,circumferential bulging disc.

[0004] Disc fissures occur rather easily after structural degeneration(a part of the aging process that may be accelerated by trauma) offibrous components of the annulus fibrosus. Sneezing, bending or justattrition can tear these degenerated annulus fibers, creating a fissure.The fissure may or may not be accompanied by extrusion of nucleuspulposus material into or beyond the annulus fibrosus. The fissureitself may be the sole morphological change, above and beyondgeneralized degenerative changes in the connective tissue of the disc.Even if there is no visible extrusion, biochemicals within the disc maystill irritate surrounding structures. Disc fissures can bedebilitatingly painful. Initial treatment is symptomatic, including bedrest, painkillers and muscle relaxants. More recently spinal fusion withcages have been performed when conservative treatment did not relievethe pain. The fissure may also be associated with a herniation of thatportion of the annulus.

[0005] With a contained disc herniation, there are no free nucleusfragments in the spinal canal. Nevertheless, even a contained discherniation is problematic because the outward protrusion can press onthe spinal nerves or irritate other structures. In addition to nerveroot compression, escaped nucleus pulposus contents may chemicallyirritate neural structures. Current treatment methods include reductionof pressure on the annulus by removing some of the interior nucleuspulposus material by percutaneous nuclectomy. However, complicationsinclude disc space infection, nerve root injury, hematoma formation,instability of the adjacent vertebrae and collapse of the disc fromdecrease in height.

[0006] Another disc problem occurs when the disc bulges outwardcircumferentially in all directions and not just in one location. Overtime, the disc weakens and takes on a “roll” shape or circumferentialbulge. Mechanical stiffness of the joint is reduced and the joint maybecome unstable. One vertebra may settle on top of another. This problemcontinues as the body ages and accounts for shortened stature in oldage. With the increasing life expectancy of the population, suchdegenerative disc disease and impairment of nerve function are becomingmajor public health problems. As the disc “roll” extends beyond thenormal circumference, the disc height may be compromised, foramina withnerve roots are compressed. In addition, osteophytes may form on theouter surface of the disc roll and further encroach on the spinal canaland foramina through which nerves pass. This condition is called lumbarspondylosis.

[0007] It has been thought that such disc degeneration creates segmentalinstability which disturbs sensitive structures which in turn registerpain. Traditional, conservative methods of treatment include bed rest,pain medication, physical therapy or steroid injection. Upon failure ofconservative therapy, spinal pain (assumed to be due to instability) hasbeen treated by spinal fusion, with or without instrumentation, whichcauses the vertebrae above and below the disc to grow solidly togetherand form a single, solid piece of bone. The procedure is carried outwith or without discectomy. Other treatments include discectomy alone ordisc decompression with or without fusion. Nuclectomy can be performedby removing some of the nucleus to reduce pressure on the annulus.However, complications include disc space infection, nerve root injury,hematoma formation, and instability of adjacent vertebrae.

[0008] These interventions have been problematic in that alleviation ofback pain is unpredictable even if surgery appears successful. Inattempts to overcome these difficulties, new fixation devices have beenintroduced to the market, including but not limited to pedicle screwsand interbody fusion cages. Although pedicle screws provide a highfusion success rate, there is still no direct correlation between fusionsuccess and patient improvement in function and pain. Studies on fusionhave demonstrated success rates of between 50% and 67% for painimprovement, and a significant number of patients have more painpostoperatively. Therefore, different methods of helping patients withdegenerative disc problems need to be explored.

[0009] FIGS. 1(a) and 1(b) illustrate a cross-sectional anatomical viewof a vertebra and associated disc and a lateral view of a portion of alumbar and thoracic spine, respectively. Structures of a typicalcervical vertebra (superior aspect) are shown in FIG. 1(a): 104—lamina:106—spinal cord: 108—dorsal root of spinal nerve; 114—ventral root ofspinal nerve; 116—posterior longitudinal ligament: 118—intervertebraldisc; 120—nucleus pulposus; 122—annulus fibrosus; 124—anteriorlongitudinal ligament; 126—vertebral body; 128—pedicle; 130—vertebralartery; 132—vertebral veins; 134—superior articular facet; 136—posteriorlateral portion of the annulus; 138—posterior medial portion of theannulus; and 142—spinous process. In FIG. 1(a), one side of theintervertebral disc 118 is not shown so that the anterior vertebral body126 can be seen. FIG. 1(b) is a lateral aspect of the lower portion of atypical spinal column showing the entire lumbar region and part of thethoracic region and displaying the following structures:118—intervertebral disc; 126—vertebral body; 142—spinous process;170—inferior vertebral notch; 10—spinal nerve; 174—superior articularprocess; 176—lumbar curvature; and 180—sacrum.

[0010] The presence of the spinal cord and the posterior portion of thevertebral body, including the spinous process, and superior and inferiorarticular processes, prohibit introduction of a needle or trocar from adirectly posterior position. This is important because the posteriordisc wall is the site of symptomatic annulus tears and discprotrusions/extrusions that compress or irritate spinal nerves for mostdegenerative disc syndromes. The inferior articular process, along withthe pedicle and the lumbar spinal nerve, form a small “triangular”window (shown in black in FIG. 1(c)) through which introduction can beachieved from the posterior lateral approach. FIG. 1(d) looks down on aninstrument introduced by the posterior lateral approach. It is wellknown to those skilled in the art that percutaneous access to the discis achieved by placing an introducer into the disc from this posteriorlateral approach, but the triangular window does not allow much room tomaneuver. Once the introducer pierces the tough annulus fibrosus, theintroducer is fixed at two points along its length and has very littlefreedom of movement. Thus, this approach has allowed access only tosmall central and anterior portions of the nucleus pulposus. Currentmethods do not permit percutaneous access to the posterior half of thenucleus or to the posterior wall of the disc. Major and potentiallydangerous surgery is required to access these areas.

[0011] U.S. Pat. No. 5,433,739 (the “'739 patent”) discloses placementof an RF electrode in an interior region of the disc approximately atthe center of the disc. RF power is applied, and heat then putativelyspreads out globally throughout the disc. The '739 patent teaches theuse of a rigid shaft which includes a sharpened distal end thatpenetrates through the annulus fibrosus and into the nucleus pulposus.In one embodiment the shaft has to be rigid enough to permit the distalend of the RF electrode to pierce the annulus fibrosus, and the abilityto maneuver its distal end within the nucleus pulposus is limited. Inanother embodiment, a somewhat more flexible shaft is disclosed.However, neither embodiment of the devices of the '739 patent permitsaccess to the posterior, posterior lateral and posterior medial regionof the disc, nor do they provide for focal delivery of therapy to aselected local region within the disc or precise temperature control atthe annulus. The '739 patent teaches the relief of pain by globallyheating the disc. There is no disclosure of treating an annular tear orfissure.

[0012] U.S. Pat. No. 5,201,729 (the “'729 patent”) discloses the use ofan optical fiber that is introduced into a nucleus pulposus. In the '729patent, the distal end of a stiff optical fiber shaft extends in alateral direction relative to a longitudinal axis of an introducer. Thisprevents delivery of coherent energy into the nucleus pulposus in thedirection of the longitudinal axis of the introducer. Due to theconstrained access from the posterior lateral approach, stiff shaft andlateral energy delivery, the device of the '729 patent is unable to gainclose proximity to selected portion(s) of the annulus (i.e., posterior,posterior medial and central posterior) requiring treatment or toprecisely control the temperature at the annulus. No use in treating anannular fissure is disclosed. The device of the '729 patent describesablating the nucleus pulposus.

[0013] Accordingly, it is desirable to diagnose and treat discabnormalities at locations previously not accessible via percutaneousapproaches and without substantial destruction to the disc. It wouldfurther be desirable to be able to administer materials to a precise,selected location within the disc, particularly to the location of theannular fissure. It would be further desirable to provide thermal energyinto collagen in the area of the fissure to strengthen the annulus andpossibly fuse collagen to the sides of the fissure, particularly at theposterior, posterior lateral and the posterior medial regions of theinner wall of the annulus fibrosus.

SUMMARY

[0014] Accordingly, one aspect of the invention features a minimallyinvasive method and apparatus for diagnosing and treating fissures ofdiscs at selected locations within the disc.

[0015] Another aspect features an apparatus which is advanceable andnavigable at the inner wall of the annulus fibrosus to provide localizedheating at the site of the annular fissure.

[0016] Another aspect features a method and apparatus to treatdegenerative intervertebral discs by delivering thermal energy to atleast a portion of the nucleus pulposus to reduce water content of thenucleus pulposus and shrink the nucleus pulposus.

[0017] Still a further aspect features a device which has a distal endthat is inserted into the disc and accesses the posterior, posteriorlateral and the posterior medial regions of the inner wall of theannulus fibrosus in order to repair or shrink an annular fissure at sucha location.

[0018] Methods for manipulating a disc tissue with a fissure or tear inan intervertebral disc, the disc having a nucleus pulposus and anannulus fibrosus, the annulus having an inner wall of the annulusfibrosus, employ an externally guidable intervertebral disc apparatus,or catheter. The procedure is performed with a catheter having a distalend, a proximal end, a longitudinal axis, and an intradiscal section atthe catheter's distal end on which there is at least one functionalelement. The catheter is advanced through the nucleus pulposus andaround an inner wall of an annulus fibrosus by applying a force to theproximal end but the applied force is insufficient for the intradiscalsection to puncture the annulus fibrosus. The next step is positioningthe functional element at a selected location of the disc by advancingor retracting the catheter and optionally twisting the proximal end ofthe catheter. Then the functional unit treats the annular fissure.

[0019] A method of treating an intervertebral fissure includes placingan energy source adjacent to the fissure and providing sufficient energyto the fissure to raise the temperature to at least about 45-70° C. andfor a sufficient time to cause the collagen to weld.

[0020] Yet another method of treating an intervertebral fissure includesplacing a catheter with a lumen adjacent to the fissure and injectingsealant into the fissure via the catheter lumen to seal the fissure.

[0021] In addition to the methods, there is provided an externallyguidable intervertebral disc apparatus for diagnosis or manipulation ofdisc tissue present at a selected location of an intervertebral disc,the disc having a nucleus pulposus, an annulus fibrosus, and an innerwall of the annulus fibrosus, the nucleus pulposus having a diameter ina disc plane between opposing sections of the inner wall. The apparatuscomprises a catheter having a distal end, a proximal end, and alongitudinal axis, and an intradiscal section at the catheter's distalend, which is extendible into the disc, has sufficient rigidity to beadvanceable through the nucleus pulposus and around the inner wall ofthe annulus fibrosus under a force applied longitudinally to theproximal end, has sufficient flexibility in a direction of the discplane to be compliant with the inner wall, and has insufficientpenetration ability to be advanceable out through the annulus fibrosusunder the force; and a functional element located at the intradiscalsection for adding sufficient thermal energy at or near the fissure.

[0022] According to another aspect of the invention, an intervertebraldisc apparatus includes an introducer and a catheter. The introducerincludes an introducer lumen. The catheter is at least partiallypositionable in the introducer lumen. The catheter includes anintradiscal section and an energy delivery device coupled to theintradiscal section. The intradiscal section is configured to beadvanceable through a nucleus pulposus of the intervertebral disc andpositionable adjacent to a selected site of an inner wall of an annulusfibrosus. Embodiments of this aspect may include that the energydelivery device is configured to deliver sufficient energy to, e.g.,create a selected ablation of a selected site of the intervertebraldisc, reduce an intradiscal pressure of the intervertebral disc, and/orprovide a denervation of a nerve at a selected site of theintervertebral disc. The energy delivery device includes, e.g., an RFelectrode configured to be coupled to an RF energy source.

[0023] According to another aspect of the invention, a method oftreating back or neck pain includes providing a catheter deployable froman introducer lumen, the catheter including an intradiscal sectioncoupled to an energy delivery device, wherein the intradiscal section isadvanceable through a nucleus pulposus and positionable along a selectedsite of an inner wall of an annulus fibrosus. The method includesadvancing the intradiscal section into the nucleus pulposus from adistal end of the introducer lumen and positioning at least a portion ofthe intradiscal section along at least a portion of the inner wall ofthe annulus fibrosus to the selected site. Embodiments of this aspectmay include delivering sufficient energy from the energy delivery deviceto, e.g., create a selected ablation of a selected site of theintervertebral disc, reduce an intradiscal pressure of theintervertebral disc and/or denervate a nerve of the intervertebral disc.

[0024] Another aspect features an intervertebral disc apparatusincluding a catheter at least partially positionable in an introducerlumen. The catheter includes an intradiscal section and an energydelivery device coupled to the intradiscal section. The intradiscalsection is configured to be advanceable through a nucleus pulposus ofthe intervertebral disc and navigationable along an inner wall of anannulus fibrosus. Embodiments of this aspect of the invention mayinclude multiple electrodes that operate in a bipolar mode.

[0025] The details of one or more embodiments are set forth in thedrawings and the description below. Other features will be apparent fromthe description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

[0026]FIG. 1(a) is a superior cross-sectional anatomical view of acervical disc and vertebra.

[0027]FIG. 1(b) is a lateral anatomical view of a portion of a lumbarspine.

[0028]FIG. 1(c) is a posterior-lateral anatomical view of two lumbarvertebrae and illustration of the triangular working zone.

[0029]FIG. 1(d) is a superior cross-sectional view of the requiredposterior lateral approach.

[0030]FIG. 2 is a second cross-sectional view of an intervertebral discillustrating a disc plane of the intervertebral disc and aninferior/superior plane.

[0031]FIG. 3(a) is a plan view of an introducer and an instrument of theinvention in which solid lines illustrate the position of the instrumentin the absence of bending forces and dotted lines indicate the positionthe distal portion of the instruments would assume under bending forcesapplied to the intradiscal section of the instrument.

[0032]FIG. 3(b) is an end view of the handle of the embodiment shown inFIG. 3(a).

[0033]FIG. 4 is a cross-sectional view of an intervertebral disc with aportion of the intervertebral apparatus of the present inventioninserted in the intervertebral disc.

[0034]FIG. 5(a) is a cross-sectional view of the intervertebral segmentof the embodiment of the invention shown in FIG. 3(a) taken along theline 5(a)-5(a) of FIG. 3(a).

[0035]FIG. 5(b) is a cross-sectional view of the intervertebral segmentof a second embodiment of the present invention having a combinedwall/guiding mandrel.

[0036]FIG. 6 is a perspective view of an embodiment of an apparatus ofthe present invention with a resistive heating coil positioned around anexterior of an intradiscal section of the catheter.

[0037]FIG. 7 is a partial cross-sectional view of an embodiment anapparatus of the invention illustrating a sensor positioned in aninterior of the intradiscal section of the catheter.

[0038]FIG. 8 is a partial cross-sectional view of an embodiment of theapparatus of the invention further including a sheath positioned aroundthe resistive heating coil.

[0039]FIG. 9 is a partial cross-sectional view of an embodiment of theapparatus of FIG. 6 with multiple resistive heating coils.

[0040]FIG. 10 is a plan view of an embodiment of the intradiscal sectionof a catheter of the invention with a helical structure.

[0041]FIG. 11 is a block diagram of an open or closed loop feedbacksystem that couples one or more sensors to an energy source.

[0042]FIG. 12 is a block diagram of an embodiment illustrating an analogamplifier, analog multiplexer and microprocessor used with the feedbackcontrol system of FIG. 11.

DETAILED DESCRIPTION

[0043] The present invention provides a method and apparatus fordiagnosing and treating intervertebral disc disorders, such as, forexample, tears of fissures of the annulus fibrosus, herniations, andcircumferential bulging, which may or may not be accompanied withcontained or escaped extrusions.

[0044] In general, an apparatus of the invention is in the form of anexternally guidable intervertebral disc apparatus for accessing andmanipulating disc tissue present at a selected location of anintervertebral disc having a nucleus pulposus and an annulus fibrosus,the annulus having an inner wall. Use of a temperature-controlled energydelivery element, combined with the navigational control of theinventive catheter, provides preferential, localized heating to treatthe fissure. For ease of reference to various manipulations anddistances described below, the nucleus pulposus can be considered ashaving a given diameter in a disc plane between opposing sections of theinner wall. This nucleus pulposus diameter measurement allows instrumentsizes (and parts of instruments) designed for one size disc to bereadily converted to sizes suitable for an instrument designed for adifferent size of disc.

[0045] The operational portion of the apparatus of the invention isbrought to a location in or near the disc's fissure using techniques andapparatuses typical of percutaneous interventions. For convenience andto indicate that the apparatus of the invention can be used with anyinsertional apparatus that provides proximity to the disc, includingmany such insertional apparatuses known in the art, the term“introducer” is used to describe this aid to the method. An introducerhas an internal introducer lumen with a distal opening at a terminus ofthe introducer to allow insertion (and manipulation) of the operationalparts of the apparatus into (and in) the interior of a disc.

[0046] The operational part of the apparatus comprises an elongatedelement referred to as a catheter, various parts of which are located byreference to a distal end and a proximal end at opposite ends of itslongitudinal axis. The proximal end is the end closest to the externalenvironment surrounding the body being operated upon (which may still beinside the body in some embodiments if the catheter is attached to ahandle insertable into the introducer). The distal end of the catheteris intended to be located inside the disc under conditions of use. Thecatheter is not necessarily a traditional medical catheter (i.e., anelongate hollow tube for admission or removal of fluids from an internalbody cavity) but is a defined term for the purposes of thisspecification. “Catheter” has been selected as the operant word todescribe this part of the apparatus, as the inventive apparatus is along, flexible tube which transmits energy and/or material from alocation external to the body to a location internal to the disc beingaccessed upon, such as a collagen solution and heat to the annularfissure. Alternatively, material can be transported in the otherdirection to remove material from the disc, such as removing material byaspiration to decrease pressure which is keeping the fissure open andaggravating the symptoms due to the fissure. Material may be removed todecrease intradiscal pressure which maintains a herniation.

[0047] The catheter is adapted to slidably advance through theintroducer lumen, the catheter having an intradiscal section at thedistal end of the catheter, the intradiscal section being extendiblethrough the distal opening at the terminus of the introducer into thedisc. Although the length of the intradiscal portion can vary with theintended function as explained in detail below, a typical distance ofextension is at least one-half the diameter of the nucleus pulposus,preferably in the range of one-half to one and one-half times thecircumference of the nucleus pulposus.In order that the functionalelements of the catheter can be readily guided to the desired locationwithin a disc, the intradiscal portion of the catheter is manufacturedwith sufficient rigidity to avoid collapsing upon itself while beingadvanced through the nucleus pulposus and navigated around the innerwall of the annulus fibrosus. The intradiscal portion, however, hasinsufficient rigidity to puncture the annulus fibrosus under the sameforce used to advance the catheter through the nucleus pulposus andaround the inner wall of the annulus fibrosus. Absolute penetrationability will vary with sharpness and stiffness of the tip of thecatheter, but in all cases a catheter of the present invention willadvance more readily through the nucleus pulposus than through theannulus fibrosus.

[0048] In preferred embodiments, the intradiscal section of the catheterfurther has differential bending ability in two orthogonal directions atright angles to the longitudinal axis. This causes the catheter to bendalong a desired plane (instead of at random). Also when a torsional(twisting) force is applied to the proximal end of the catheter tore-orient the distal end of the catheter, controlled advancement of thecatheter in the desired plane is possible.

[0049] A further component of the catheter is a functional elementlocated in the intradiscal section for diagnosis or for adding energyand adding and/or removing material at the selected location of the discwhere the annular tear is to be treated, or some other therapeuticaction is to be carried out. The apparatus allows the functional elementto be controllably guided by manipulation of the proximal end of thecatheter into a selected location for localized diagnosis and/ortreatment of a portion of the disc, such as, for example, the annularfissure.

[0050] The method of the invention which involves manipulating disctissue at the annular fissure or other selected location, is easilycarried out with an apparatus of the invention. An introducer isprovided that is located in a patient's body so that its proximal end isexternal to the body and the distal opening of its lumen is internal tothe body and (1) internal to the annulus fibrosus or (2) adjacent to anannular opening leading to the nucleus pulposus, such as an annular tearor trocar puncture that communicates with the nucleus pulposus. Thecatheter is then slid into position in and through the introducer lumenso that the functional element in the catheter is positioned at theselected location of the disc by advancing or retracting the catheter inthe introducer lumen and optionally twisting the proximal end of thecatheter to precisely navigate the catheter. By careful selection of therigidity of the catheter and by making it sufficiently blunt to notpenetrate the annulus fibrosus, and by careful selection of theflexibility in one plane versus the orthogonal plane, the distal portionof the catheter will curve along the inner wall of the annulus fibrosusas it is navigated and is selectively guided to an annular tear or otherselected location(s) in the disc. Energy is applied and/or material isadded or removed at the selected location of the disc via the functionalelement.

[0051] Each of the elements of the apparatus and method will now bedescribed in more detail. However, a brief description of disc anatomyis provided first, as sizes and orientation of structural elements ofthe apparatus and operations of the method can be better understood insome cases by reference to disc anatomy.

[0052] The annulus fibrosus is comprised primarily of tough fibrousmaterial, while the nucleus pulposus is comprised primarily of anamorphous colloidal gel. There is a transition zone between the annulusfibrosus and the nucleus pulposus made of both fibrous-like material andamorphous colloidal gel. The border between the annulus fibrosus and thenucleus pulposus becomes more difficult to distinguish as a patientages, due to degenerative changes. This process may begin as early as 30years of age. For purposes of this specification, the inner wall of theannulus fibrosus can include the young wall comprised primarily offibrous material as well as the transition zone which includes bothfibrous material and amorphous colloidal gels (hereafter collectivelyreferred to as the “inner wall of the annulus fibrosus”). Functionally,that location at which there is an increase in resistance to catheterpenetration and which is sufficient to cause bending of the distalportion of the catheter into a radius less than that of the internalwall of the annulus fibrosus is considered to be the “inner wall of theannulus fibrosus”.

[0053] As with any medical instrument and method, not all patients canbe treated, especially when their disease or injury is too severe. Thereis a medical gradation of degenerative disc disease (stages 1-5). See,for example, Adams et al., “The Stages of Disc Degeneration as Revealedby Discograms,” J. Bone and Joint Surgery, 68, 36-41 (1986). As thesegrades are commonly understood, the methods of instrument navigationdescribed herein would probably not be able to distinguish between thenucleus and the annulus in degenerative disease of grade 5. In any case,most treatment is expected to be performed in discs in stages 3 and 4,as stages 1 and 2 are asymptomatic in most patients, and stage 5 mayrequire disc removal and fusion.

[0054] Some of the following discussion refers to motion of the catheterinside the disc by use of the terms “disc plane” “oblique plane” and“cephalo-caudal plane.” These specific terms refer to orientations ofthe catheter within the intervertebral disc. Referring now to FIG. 2(which shows a vertical cross-section of a disc), a disc plane 30 of theintervertebral disc is generally a plane of some thickness 27 within thenucleus pulposus 120 orthogonal to the axis formed by the spinal column(i.e., such a disc plane is substantially horizontal in a standinghuman, corresponding to the “flat” surface of a vertebra). A obliqueplane 31 extends along any tilted orientation relative to axial plane30; however, when the plane is tilted 90°, such a plane would besubstantially vertical in a standing human and is referred to as acephalo-caudal plane. Reference is made to such planes to describecatheter movements with respect to the disc plane. In variousembodiments, disc plane 30 has a thickness no greater than the thicknessof the intervertebral disc, preferably a thickness no greater than 75%of a thickness of the intervertebral disc, and more preferably athickness no greater than 50% of a thickness of the intervertebral disc.Movement of the intradiscal portion 16 of catheter 14 is confined withina disc plane by the physical and mechanical properties of theintradiscal portion 16 during advancement of the catheter when thebending plane of the catheter is aligned with the disc plane until someadditional force is applied to the catheter by the physician. A twistingforce (which can be applied mechanically, electrically, or by any othermeans) acting on the proximal end of the catheter changes the forcesacting on the distal end of the catheter so that the plane of thecatheter bend can be angled relative to the disc plane as the catheteris advanced. Thus, the physician can cause the distal end of thecatheter to move up or down, depending on the direction of the twist.

[0055] Turning now to the introducer, a detailed description of anentire apparatus should not be necessary for those skilled in the art ofpercutaneous procedures and the design of instruments intended for suchuse. The method of the invention can also be carried out with endoscopicinstruments, and an endoscopic apparatus having structural parts thatmeet the descriptions set forth in this specification would also be anapparatus of the invention.

[0056] In general, a device of the invention can be prepared in a numberof different forms and can consist (for example) of a single instrumentwith multiple internal parts or a series of instruments that can bereplaceably and sequentially inserted into a hollow fixed instrument(such as a needle) that guides the operational instruments to a selectedlocation, such as, for example, an annular fissure, in or adjacent to anintervertebral disc. Because prior patents do not fully agree on how todescribe parts of percutaneous instruments, terminology with the widestcommon usage will be used.

[0057] The introducer, in its simplest form, can consist of a hollowneedle-like device (optionally fitted with an internal removableobturator or trocar to prevent clogging during initial insertion) or acombination of a simple exterior cannula that fits around a trocar. Theresult is essentially the same: placement of a hollow tube (the needleor exterior cannula after removal of the obturator or trocar,respectively) through skin and tissue to provide access into the annulusfibrosus. The hollow introducer acts as a guide for introducinginstrumentation. More complex variations exist in percutaneousinstruments designed for other parts of the body and can be applied todesign of instruments intended for disc operations. Examples of suchobturators are well known in the art. A particularly preferredintroducer is a 17- or 18-gauge, thin-wall needle with a matchedobturator, which after insertion is replaced with a catheter of thepresent invention.

[0058] Referring now to the figures, FIGS. 3(a) and 3(b) illustrate oneembodiment of a catheter 14 of the invention as it would appear insertedinto an introducer 12. The apparatus shown is not to scale, as anexemplary apparatus (as will be clear from the device dimensions below)would be relatively longer and thinner; the proportions used in FIG.3(a) were selected for easier viewing by the reader. The distal portionof an intervertebral apparatus operates inside an introducer 12 havingan internal introducer lumen 13. A flexible, movable catheter 14 is atleast partially positionable in the introducer lumen 13. Catheter 14includes a distal end section 16 referred to as the intradiscal section,which is designed to be the portion of the catheter that will be pushedout of the introducer lumen and into the nucleus pulposus, wheremovement of the catheter will be controlled to bring operationalportions of the catheter into the selected location(s) within the disc,such as, for example, the annular tear. In FIG. 3(a), dashed lines areused to illustrate bending of the intradiscal portion of the catheter asit might appear under use, as discussed in detail later in thespecification. FIG. 3(b) shows an end view of handle 11 at the proximalend of the catheter, with the handle 11 having an oval shape to indicatethe plane of bending, also discussed in detail later in thespecification. Other sections and properties of catheter 14 aredescribed later.

[0059] For one embodiment suitable for intervertebral discs, the outerdiameter of catheter 14 is in the range of 0.2 to 5 mm, the total lengthof catheter 14 (including the portion inside the introducer) is in therange of 10 to 60 cm, and the length of introducer 12 is in the range of5 to 50 cm. For one preferred embodiment, the catheter has a diameter of1 mm, an overall length of 30 cm, and an introduced length of 15 cm (forthe intradiscal section). With an instrument of this size, a physiciancan insert the catheter for a distance sufficient to reach selectedlocation(s) in the nucleus of a human intervertebral disc.

[0060]FIG. 4 illustrates the anatomy of an intervertebral disc and showsan apparatus of the invention inserted into a disc. Structures of thedisc are identified and described by these anatomical designations: theposterior lateral inner annulus 136, posterior medial inner annulus 138,annulus fibrosus 122/nucleus pulposus 120 interface, the annulus/duralinterface 146, annulus/posterior longitudinal ligament interface 148,anterior lateral inner annulus 150, and the anterior medial innerannulus 152.

[0061] Referring again to FIG. 4, the mechanical characteristics ofintradiscal section 16 of catheter 14 are selected to have (1)sufficient column strength along the longitudinal axis of the catheterto avoid collapse of the catheter and (2) different flexural strengthsalong the two axes orthogonal to the longitudinal axis to allowcontrolled bending of the catheter. These parameters make the catheterconformable and guidable along inner wall 22 of an annulus fibrosus 122to reach selected location(s), such as the posterior medial annulus 138.

[0062] Specific mechanical characteristics of particular designs will bedescribed later in the examples that follow. Generally, however, thenecessary design features can be selected (in an interrelated fashion)by first providing the intradiscal section of the catheter withsufficient column strength to be advanceable through normal humannucleus pulposus and around the inner wall of the annulus fibrosuswithout collapse. Here “collapse” refers to bending sufficient toinhibit further advancement at the tip. Advancement of the tip isrestricted by 1) sliding through the normal gelatinous nucleus pulposus,2) contacting denser clumps of nucleus pulposus and 3) curving andadvancing along the inner wall of the annulus. Column strength can beincreased in many ways known in the art, including but not limited toselecting materials (e.g., metal alloy or plastic) with a highresistance to bending from which to form the catheter, forming thestructure of the catheter with elements that add stiffening (such asbracing), and increasing the thickness of the structural materials.Column strength can be decreased to favor bending by selecting theopposite characteristics (e.g., soft alloys, hinging, and thinstructural elements).

[0063] When the catheter collapses, the physician feels an abruptdecrease in resistance. At that time, the catheter forms one or moreloops or kinks between the tip of the introducer and the distal tip ofthe catheter.

[0064] Particularly preferred for locations, such as, for example,annular tears, at the posterior of the annulus, the tip 28 ofintradiscal section 16 is biased or otherwise manufactured so that itforms a pre-bent segment prior to contact with the annulus fibrosus asshown in FIG. 3(a). The bent tip will cause the intradiscal section totend to continue to bend the catheter in the same direction as thecatheter is advanced. This enhanced curving of a pre-bent catheter ispreferred for a catheter that is designed to reach a posterior region ofthe nucleus pulposus; however, such a catheter must have sufficientcolumn strength to prevent the catheter from collapsing back on itself.

[0065] The intradiscal section not only must allow bending around therelatively stronger annulus fibrosus in one direction, but also resistbending in the orthogonal direction to the plane in which bending isdesigned to occur. By twisting the proximal end of a catheter and thuscontrolling the orientation of the plane of bending while concurrentlycontrolling the advancement of the catheter through the nucleus, aphysician can navigate the catheter and its instrumentation within thedisc.

[0066] The bending stiffness of the intradiscal section as measured inTaber stiffness units (using a length of the inventive catheter as thetest strip rather than the standard dimension, homogeneous-material teststrip) should be in the range of 2-400 units (in a 0-10,000 unit range)in the desired bending plane, preferably 3-150 units. In preferredembodiments, stiffness is in the range of 4-30 units in the desiredbending plane. In all cases, the bending stiffness preferably is 2-20times higher for bending in the orthogonal direction.

[0067] The column or compressive strength of the intradiscal section(force required to buckle a segment whose length is 25 or more times itsdiameter) is in the range of 0.05 to 4 kg, preferably 0.05 to 2 kg. Inthe most preferred embodiments, it is in the range of 0.1 to 1 kg. Inthe proximal shaft section (i.e., the part of the catheter proximal tothe intradiscal section), this strength is in the range of 0.1 to 25 kg,preferably 0.2 to 7 kg. In the most preferred embodiments, it is in therange of 0.7 to 4 kg.

[0068] Returning now to FIG. 4, intradiscal section 16 is guidable andcan reach the posterior, the posterior lateral, and the posterior medialregions of the posterior wall of the annulus fibrosus, as well as otherselected section(s) on or adjacent to inner wall 22. In order to movethe functional section of the catheter into a desired nucleus location,intradiscal section 16 is first positioned in the nucleus pulposus 120by means of the introducer.

[0069] In most uses, introducer 12 pierces annulus fibrosus 122 and isadvanced through the wall of the annulus fibrosus into the nucleuspulposus. In such embodiments, introducer 12 is then extended a desireddistance into nucleus pulposus 120. Catheter 14 is advanced through adistal end of introducer 12 into nucleus pulposus 120. Advancement ofthe catheter 14, combined with increased resistance to advancement atthe annulus fibrosus, causes the tip of the intradiscal section to bendrelative to the longitudinal axis of introducer 12 when the intradiscalsection contacts the inner wall of the annulus fibrosus 122. Catheter 14is navigated along inner wall 22 of annulus fibrosus 122 to selectedsite(s) of inner wall 22 or within nucleus pulposus 120. For example,intradiscal section 16 can be positioned in or adjacent to a fissure ortear 44 of annulus fibrosus 122.

[0070] The distal portion 28 of intradiscal section 16 is designed to beincapable of piercing the annulus fibrosus 122. The inability of distalportion 28 to pierce the annulus can be the result of either shape ofthe tip 29 or flexibility of distal portion 28, or both. The tip 29 isconsidered sufficiently blunt when it does not penetrate the annulusfibrosus but is deflected back into the nucleus pulposus or to the sidearound the inner wall of the annulus when the tip 29 is advanced. Thetip can be made with a freely rotating ball. This embodiment providesnot only a blunt surface but also a rolling contact to facilitatenavigation.

[0071] Many percutaneous and endoscopic instruments designed for otherpurposes can be adapted for use in this invention. This permits otherfunctions at the desired location after the catheter is advanced to thatposition. For example, cutting edges and sharp points can be present inthe distal portion 28 if they can be temporarily masked by a coveringelement. However, such devices must be sufficiently flexible and thin tomeet the design characteristics described in this specification.

[0072] In another embodiment an introducer 12 pierces the skin andreaches an exterior of annulus fibrosus 122. A rigid and sharp trocar isthen advanced through introducer 12, to pierce annulus fibrosus 122 andenter the disc. The trocar is then removed and catheter 14 is advancedthrough a distal end of introducer 12, following the path created by thetrocar in annulus fibrosus 122 beyond the end of the introducer. In suchcases, the introducer is outside the annulus fibrosus 122 and only thecatheter with its guidable distal portion 16 is present inside the disc.The physician can manipulate the proximal portion 15 of the catheter tomove the distal portion of the catheter to a selected location fordiagnosing or treating the nucleus pulposus 120 or the inner wall 22 ofthe annulus fibrosus 122, such as, for example, a fissure of the annulusfibrosus 122.

[0073] Catheter 14 is not always pre-bent as shown in FIG. 3(a), butoptionally can include a biased distal portion 28 if desired. “Pre-bent”or “biased” means that a portion of the catheter (or other structuralelement under discussion) is made of a spring-like material that is bentin the absence of external stress but which under selected stressconditions (for example, while the catheter is inside the introducer),is linear. Such a biased distal portion can be manufactured from eitherspring metal or superelastic memory material (such as Tinel®nickel-titanium alloy, Raychem Corp., Menlo Park Calif.). The introducer(at least in the case of a spring-like material for forming thecatheter) is sufficiently strong to resist the bending action of thebent tip and maintain the biased distal portion in alignment as itpasses through the introducer. Compared to unbiased catheters, acatheter with a biased distal portion 28 encourages advancement ofintradiscal section 16 substantially in the direction of the bendrelative to other lateral directions as shown by the bent location ofintradiscal section 16 indicated by dashed lines in FIG. 3(a). That is,biased distal portion 28 permits advancement of intradiscal section 16substantially in only one lateral direction relative to the longitudinalaxis of introducer 12. More generally, embodiments of the intradiscalsection may resist bending in at least one direction. Biasing thecatheter tip also further decreases likelihood that the tip 29 will beforced through the annulus fibrosus under the pressure used to advancethe catheter.

[0074] In one embodiment, the outer diameter of catheter 14 is in therange of 0.01 to 0.200 inches, the total length of catheter 14 is in therage of 5 to 24 inches, and the length of introducer 12 is 2 to 20inches. The total length of catheter 14 (including the portion insidethe introducer) may be in the range of 5 to 24 inches, and the length ofintroducer 12 may be 2 to 20 inches. The intradiscal section may have alength at least one-half of the diameter of the nucleus pulposus. Oneembodiment of the introducer is an 18- or 17-gauge, thin-wall needlewith a matched stylet.

[0075] In addition to biasing a catheter tip prior to insertion into anintroducer, a catheter tip can be provided that is deflected bymechanical means, such as a wire attached to one side of the tip thatdeflects the tip in the desired direction upon application of force tothe proximal end of the deflection wire. Any device in which bending ofthe tip of a catheter of the invention is controlled by the physician is“actively steerable.” In addition to a tip that is actively steerable byaction of a wire, other methods of providing a bending force at the tipcan be used, such as hydraulic pressure and electromagnetic force (suchas heating a shaped memory alloy to cause it to contract). Any of anumber of techniques can be used to provide selective bending of thecatheter in one lateral direction.

[0076] Referring now to FIG. 5(a), a guiding mandrel 32 can be includedboth to add rigidity to the catheter and to inhibit movement of catheter14 in the inferior and superior directions while positioned and alignedin the disc plane of a nucleus pulposus 120. This aids the functions ofpreventing undesired contact with a vertebra and facilitatingnavigation. The mandrel can be flattened to encourage bending in a plane(the “plane of the bend”) orthogonal to the “flat” side of the mandrel.“Flat” here is a relative term, as the mandrel can have a D-shapedcross-section, or even an oval or other cross-sectional shape without aplanar face on any part of the structure. Regardless of the exactconfiguration, bending will preferentially occur in the plane formed bythe principal longitudinal axis of the mandrel and a line connecting theopposite sides of the shortest cross-sectional dimension of the mandrel(the “thin” dimension). To provide sufficient resistance to the catheterbending out of the desired plane while encouraging bending in thedesired plane, the minimum ratio is 1.25:1 (“thickest” to “thinnest”cross-sectional dimensions along at least a portion of the intradiscalsection). The maximum ratio is 20:1, with the preferred ratio beingbetween 1.5:1 and 16:3, more preferably between 2:1 and 3.5:1. Theseratios are for a solid mandrel and apply to any material, as deflectionunder stress for uniform solids is inversely proportional to thethickness of the solid in the direction (dimension) in which bending istaking place. For other types of mandrels (e.g., hollow or non-uniformmaterials), selection of dimensions and/or materials that provide thesame relative bending motions under stress are preferred.

[0077] A catheter of the present invention is designed with sufficienttorsional strength (resistance to twisting) to prevent undesireddirectional movement of the catheter. Mandrels formed from materialshaving tensile strengths in the range set forth in the examples of thisspecification provide a portion of the desired torsional strength. Othermaterials can be substituted so long as they provide the operationalfunctions described in the examples and desired operating parameters.

[0078] While the mandrel can provide a significant portion of the columnstrength, selective flexibility, and torsional strength of a catheter,other structural elements of the catheter also contribute to thesecharacteristics. Accordingly, it must be kept in mind that it is thecharacteristics of the overall catheter that determine suitability of aparticular catheter for use in the methods of the invention. Forexample, a mandrel that does not have sufficient torsional strength whenacting alone can be combined with another element, such as anti-twistingouter sheath 40 or inserting/advancing a second mandrel, to provide acatheter of the invention. Similarly, components inside the catheter,such as a heating element or potting compound, can be used to strengthenthe catheter or provide directional flexibility at the locations ofthese elements along the catheter.

[0079] It is not necessary that the guiding mandrel 32 be flattenedalong its entire length. Different mandrels can be designed fordifferent sized discs, both because of variations in disc sizes fromindividual to individual and because of variations in size from disc todisc in one patient. The bendable portion of the mandrel is preferablysufficient to allow intradiscal portion 16 of the catheter to navigateat least partially around the circumference of the inner wall of theannulus fibrosus (so that the operational functions of the catheter canbe carried out at desired location(s) along the inner wall of theannulus fibrosus). Shorter bendable sections are acceptable forspecialized instruments. In most cases, a flattened distal portion ofthe mandrel of at least 10 mm, preferably 25 mm, is satisfactory. Theflattened portion can extend as much as the entire length of themandrel, with some embodiments being flattened for less than 15 cm, inother cases for less than 10 cm, of the distal end of the guide mandrel.

[0080] The intradiscal section of the catheter can be guided to conformsufficiently to the inner wall of the annulus fibrosus to contactmultiple locations of the inner wall. The intradiscal section and/ordistal portion are positionable to any selected site around and/oradjacent to the inner wall of the annulus fibrosus for the delivery ofRF energy. The intradiscal section and/or distal portion can deliverelectromagnetic energy to, e.g., heat tissue and thereby reduce pain ata selected site (for example, any portion of the annulus fibrosus).

[0081] In preferred embodiments the guide mandrel or other differentialbending control element is maintained in a readily determinableorientation by a control element located at the proximal end of thecatheter. The orientation of the direction of bending and its amount canbe readily observed and controlled by the physician. One possiblecontrol element is simply a portion of the mandrel that extends out ofthe proximal end of the introducer and can be grasped by the physician,with a shape being provided that enables the physician to determine theorientation of the distal portion by orientation of the portion in thehand. For example, a flattened shape can be provided that mimics theshape at the distal end (optionally made larger to allow better controlin the gloved hand of the physician, as in the handle 11 of FIG. 3(b)).More complex proximal control elements capable of grasping the proximalend of the mandrel or other bending control element can be used ifdesired, including but not limited to electronic mechanical, andhydraulic controls for actuation by the physician.

[0082] The guide mandrel can also provide the function of differentialflexibility by varying the thickness in one or more dimensions (forexample, the “thin” dimension, the “thick” dimension, or both) along thelength of the mandrel. A guide mandrel that tapers (becomes graduallythinner) toward the distal tip of the mandrel will be more flexible andeasier to bend at the tip than it is at other locations along themandrel. A guide mandrel that has a thicker or more rounded tip thanmore proximal portions of the mandrel will resist bending at the tip butaid bending at more proximal locations. Thickening (or thinning) canalso occur in other locations along the mandrel. Control of thedirection of bending can be accomplished by making the mandrel moreround, i.e., closer to having 1:1 diameter ratios; flatter in differentsections of the mandrel; or by varying the absolute dimensions(increasing or decreasing the diameter). Such control over flexibilityallows instruments to be designed that minimize bending in some desiredlocations (such as the location of connector of an electrical element toavoid disruption of the connection) while encouraging bending in otherlocations (e.g., between sensitive functional elements). In this manner,a catheter that is uniformly flexible along its entire length, isvariably flexibility along its entire length, or has alternating moreflexible and less flexible segment(s), is readily obtained simply bymanufacturing the guide mandrel with appropriate thickness at differentdistances and in different orientations along the length of the mandrel.Such a catheter will have two or more different radii of curvature indifferent segments of the catheter under the same bending force.

[0083] In some preferred embodiments, the most distal 3 to 40 mm of aguide mandrel is thinner relative to central portions of the intradiscalsection to provide greater flexibility, with the proximal 10 to 40 mm ofthe intradiscal section being thicker and less flexible to add columnstrength and facilitate navigation.

[0084] The actual dimensions of the guide mandrel will vary with thestiffness and tensile strength of the material used to form the mandrel.In most cases the mandrel will be formed from a metal (elemental or analloy) or plastic that will be selected so that the resulting catheterwill have characteristics of stiffness and bending that fall within thestated limits. Additional examples of ways to vary the stiffness andtensile strength include transverse breaks in a material, advance of thematerial so that it “doubles up,” additional layers of the same ordifferent material, tensioning or relaxing tension on the catheter, andapplying electricity to a memory metal.

[0085] As illustrated in FIG. 5(b), in some embodiments of an apparatusof the invention, guiding mandrel is combined with at least a portion ofthe catheter 14 to form a structure which provides the functions ofboth, a wall/mandrel 41. In this figure, the wall/mandrel 41 of catheter14 can be varied in dimensions as described in the previous section ofthis specification directed to a separate mandrel, with the sameresulting changes in function. For example, changing the thickness ofthe wall/mandrel 41 that functions as the mandrel portion change, theflexibility and preferred direction of bending of the catheter. In manycases, the wall/mandrel 41 will be thinner than other portions of thecatheter wall 33 so that wall/mandrel 41 controls bending.Alternatively, wall/mandrel 41 can be formed of a different materialthan the other portions 33 of the catheter walls (i.e., one with a lowertensile and/or flexural strength) in order to facilitate bending.

[0086] Returning now to FIG. 5(a), the guiding mandrel 32 is generallylocated in the interior of catheter 14, where it shares space with otherfunctional elements of the catheter. For example and as shown in FIG.5(a), thermal energy delivery device lumen 34 can receive any of avariety of different couplings from an energy source 20 to a thermalenergy delivery device (functional element) further along the catheter,including but not limited to a wire or other connector between thermalenergy elements. Alternatively or concurrently, hollow lumen(s) 36 fordelivery and/or removal of a fluid or solid connectors for applicationof a force to a mechanical element can be present, so no limitationshould be placed on the types of energy, force, or material transportingelements present in the catheter. These are merely some of the possiblealternative functional elements that can be included in the intradiscalportion of the catheter. Accordingly, a general description will now begiven of some of the possible functional elements.

[0087] To facilitate a catheter in performing some function on disc ornearby tissue, such as, for example, applying electromagnetic energy tocontrollably heat disc tissue at selected location(s) inside the disc,or repairing tears or fissures in a disc by operation of the instrumentat the tear location adjacent to or inside the disc, a functionalelement is provided in or on the catheter. One such element is afunctional electromagnetic probe such as an RF electrode.

[0088] Non-limiting examples of functional elements include any elementcapable of aiding diagnosis, delivering energy, or delivering orremoving a material from a location adjacent the element's location inthe catheter, such as an opening in the catheter for delivery of a fluid(e.g., dissolved collagen to seal the fissure) or for suction, a thermalenergy delivery device (heat source), a mechanical grasping tool forremoving or depositing a solid, a cutting tool (which includes allsimilar operations, such as puncturing), a sensor for measurement of afunction (such as electrical resistance, temperature, or mechanicalstrength), or a functional element having a combination of thesefunctions.

[0089] The functional element can be at varied locations in theintradiscal portion of the catheter, depending on its intended use.Multiple functional elements can be present such as multiple functionalelements of different types (e.g., a heat source and a temperaturesensor) or multiple functional elements of the same type (e.g., multipleheat sources, such as RF elements, spaced along the intradiscalportion).

[0090] One of the functional elements present on intradiscal section 16can be an RF electrode. A variety of different types and shapes of RFelectrodes can be used. The intradiscal section electrode can bemonopolar or bipolar. In one embodiment, the RF electrode is positionedproximal to the distal portion of intradiscal section 16 so that thereis no substantial delivery of energy at the distal portion, which canthen perform other functions without being constrained by being requiredto deliver RF energy. The RF electrode is coupled to RF generatingsource 20 through the catheter. The RF electrode is positioned on anexternal surface of intradiscal section 16. A variety of different typesof electromagnetic energy can be delivered to tissue wherein heating iscaused. These include not only RF but also coherent and incoherentlight, microwave, and ultrasound.

[0091] One of the possible functional elements present on intradiscalsection 16 is a thermal energy delivery device 18. A variety ofdifferent types of thermal energy can be delivered including but notlimited to resistive heat, radiofrequency (RF), coherent and incoherentlight, microwave, ultrasound and liquid thermal jet energies. In oneembodiment, thermal energy delivery device 18 is positioned proximal tothe distal portion of intradiscal section 16 so that there is nosubstantial delivery of energy at the distal portion, which can thenperform other functions without being constrained by being required toprovide energy (or resist the resulting heat).

[0092] Some embodiments have an interior infusion lumen 36. Infusionlumen 36 is configured to transport a variety of different mediaincluding but not limited to electrolytic solutions (such as normalsaline), contrast media (such as Conray meglumine iothalamate),pharmaceutical agents, disinfectants, filling or binding materials suchas collagens or cements, chemonucleolytic agents and the like, from areservoir exterior to the patient to a desired location within theinterior of a disc (i.e., the fissure). Further, infusion lumen 36 canbe used as an aspiration lumen to remove nucleus material or excessliquid or gas (naturally present, present as the result of a liquefyingoperation, or present because of prior introduction) from the interiorof a disc. When used to transport a fluid for irrigation of the locationwithin the disc where some action is taking place (such as ablation,which generates waste materials), the infusion lumen is sometimesreferred to as an irrigation lumen. Infusion lumen 36 can be coupled tomedium reservoir 21 through the catheter (see FIG. 3(a)).

[0093] Included in the particular embodiment shown in FIG. 5(a) is oneor more sensor lumens 42. An example is a wire connecting a thermalsensor at a distal portion of the catheter to control elements attachedto a connector in the proximal handle 11 of the catheter.

[0094] Also included in the embodiment shown in FIG. 5(a) is an optionalenergy directing device 43 including but not limited to a thermalreflector, an optical reflector, thermal insulator, or electricalinsulator. Energy directing device 43 is configured to limit thermaland/or electromagnetic energy delivery to a selected site of the discand to leave other sections of the disc substantially unaffected. Energydirecting device 43 can be positioned on an exterior surface of catheterintradiscal section 16 and/or catheter 14 as well as in an internalportion of the catheter intradiscal section 16 and/or catheter 14. Forexample, the energy can be directed to the walls of the fissure tocauterize granulation tissue and to shrink the collagen component of theannulus, while the nucleus is shielded from excess heat.

[0095] In one embodiment, catheter intradiscal section 16 and/or distalportion 28 are positionable to selected site(s) around and/or adjacentto inner wall 22 of annulus fibrosus 122 for the delivery of therapeuticand/or diagnostic agents including but not limited to, electromagneticenergy, electrolytic solutions, contrast media, pharmaceutical agents,disinfectants, collagens, cements, chemonucleolytic agents and thermalenergy. Intradiscal section 16 is navigational and can reach theposterior, the posterior lateral, the posterior medial, anteriorlateral, and anterior medial regions of the annulus fibrosus, as well asselected section(s) on or adjacent to inner wall 22.

[0096] In a preferred embodiment, intradiscal section 16 is positionedadjacent to the entire posterior wall of the disc. Sufficient thermalenergy can then be delivered, for example, to selectively heat theposterior annulus to cauterize granulation tissue and shrink thecollagen component of the wail around and adjacent to fissure 44 withoutundue damage to other portions of the intervertebral disc, particularlythe nucleus. These actions help close the fissure in the annulus.

[0097] In the preferred embodiment of FIG. 5(a), markings 38 are visibleon the portion of the catheter that is located during normal operationoutside the body being acted upon, particularly for embodiments in whichthe proximal end of the catheter is designed to be directly manipulatedby the hand of the physician. Advancement of the catheter into theintroducer will advance the markings into the introducer thereby showinghow far the catheter has been advanced into the nucleus. Such a visiblemarking 38 can be positioned on an exterior surface of the catheter orcan be present on an interior surface and visible through a transparentouter covering or sheath. Preferred are visible markings everycentimeter to aid the physician in estimating the catheter tipadvancement.

[0098] If desired, visible markings can also be used to show twistingmotions of the catheter to indicate the orientation of the bending planeof the distal portion of the catheter. It is preferred, however, toindicate the distal bending plane by the shape and feel of the proximalend of the catheter assembly. The catheter can be attached to or shapedinto a handle 11 that fits the hand of the physician and also indicatesthe orientation of the distal bending plane. Both the markings and thehandle shape thus act as control elements to provide control over theorientation of the bending plane; other control elements, such asplungers or buttons that act on mechanical, hydrostatic, electrical, orother types of controls, can be present in more complex embodiments ofthe invention.

[0099] Additionally, a radiographically opaque marking device can beincluded in the distal portion of the catheter (such as in the tip or atspaced locations throughout the intradiscal portion) so that advancementand positioning of the intradiscal section can be directly observed byradiographic imaging. Such radiographically opaque markings arepreferred when the intradiscal section is not clearly visible byradiographic imaging, such as when the majority of the catheter is madeof plastic instead of metal. A radiographically opaque marking can beany of the known (or newly discovered) materials or devices withsignificant opacity. Examples include but are not limited to a steelmandrel sufficiently thick to be visible on fluoroscopy, atantalum/polyurethane tip, a gold-plated tip, bands of platinum,stainless steel or gold, soldered spots of gold and polymeric materialswith radiographically opaque filler such as barium sulfate. A resistiveheating element or an RF electrode(s) may provide sufficientradio-opacity in some embodiments to serve as a marking device.

[0100] A sheath 40 can optionally be positioned around catheter 14.Sheath 40 provides a flexible surface that is smooth and provides foreasy introduction into a selected area within the disc. Sheath 40 can bemade of a variety of different materials including but not limited topolyester, rayon, polyimide, polyurethane, polyethylene, polyamide andsilicone. When visible markings are present to indicate the advancementof the catheter, either the sheath carries the markings, or the sheathis clear to reveal markings underneath.

[0101] The thermal energy delivery device can be a known RF electrode,such as a band or coil. Heating element 46 can be an RF electrode 46positioned on and exterior of catheter 14. RF electrode 46 can bepowered by an RF generator. The thermal energy delivery device can bemade of a material that acts as an electrode. Suitable materials includebut are not limited to stainless steel or platinum. The RF electrode islocated on intradiscal section of catheter 14. Increasing levels ofcurrent conducted into the disc heats that tissue to greater temperaturelevels. A circuit can be completed substantially entirely at intradiscalsection 16 (bipolar devices) or by use of a second electrode attached toanother portion of the body (monopolar devices). In either case, acontrollable delivery of RF energy is achieved.

[0102] Using an RF electrode, sufficient energy can be delivered to theintervertebral disc to heat tissue positioned adjacent to catheter 14.The amount of tissue heating is a function of (i) the amount of currentpassing through electrode 46, (ii) the length, shape, and/or size ofheating electrode 46, (iii) the resistive properties of the tissue, and(iv) the use of cooling fluid to control temperature. The RF powersupply 20 associated with heating electrode 46 can be battery based.Catheter 14 can be sterilized and can be disposable. Design of RFelectrodes is within the skill of the art, and no special selection ofelectrode type or shape is generally required, although a particularshape or size can be selected for a particular function.

[0103] There can be two monopolar electrodes on the distal end of the RFprobe. One electrode can occupy a portion of the side of the distal endand the other can be the distal-most tip of the RF probe. The electrodescan be operated independently to provide different tissue temperatures.In one configuration, the side electrode has a smaller area than the endelectrode. If the side electrode receives the same power as the endelectrode, it will provide more concentrated current and thus willproduce more thermal energy. The end electrode will provide gentler,less concentrated current and will produce less thermal energy, forexample, to shrink collagen in the annulus without denaturing thecollagen.

[0104] In one preferred embodiment, thermal energy delivery device 18 isa resistive heating device. As illustrated in FIG. 6 a heating coil 46is positioned around an exterior of catheter 14. The heating element 46need not be in the shape of a coil. For instance, the heating elementcan be in the form of a thin flexible circuit which is mountable on orin substantially one side of the intradiscal portion of the catheter.Heating element 46 is powered by a direct current source 20 (and lesspreferably a source of alternating current). Heating element is made ofa material that acts as a resistor. Suitable materials include but arenot limited to stainless steel, nickel/chrome alloys, platinum, and thelike.

[0105] Preferably, the heating element is inside the intradiscal sectionof catheter 14 (FIG. 8). The resistive material is electricallyinsulated and substantially no current escapes into the body. Withincreasing levels of current, element 46 heats to greater temperaturelevels. Additionally, a circuit can be completed substantially entirelyat intradiscal section 16 and a controllable delivery of thermal energyis achieved. In one embodiment, 2 watts pass through heating element 46to produce a temperature of about 55° C. in a selected target such asfissure 44, 3 watts produces 65° C., 4 watts produces 75° C. and so on.

[0106] In another embodiment, thermal energy delivery device 18 is aradiofrequency electrode, such as a band or coil. As illustrated in FIG.6, RF electrode 46 is positioned on an exterior of catheter 14. RFelectrode 46 is powered by an RF generator. The electrode is made ofsuitable materials including but not limited to stainless steel orplatinum. The RF electrode is located on intradiscal section of catheter14. Increasing levels of current conducted into disc tissue heat thattissue to greater temperature levels. A circuit can be completedsubstantially entirely at intradiscal section 16 (bipolar device) or byuse of a second electrode attached to another portion of the patient'sbody (monopolar device). In either case, a controllable delivery of RFenergy is achieved.

[0107] In another embodiment sufficient energy is delivered to theintervertebral disc to heat and shrink the collagen component of theannulus but not ablate tissue adjacent to catheter 14.

[0108] With a resistive heating device, the amount of thermal energydelivered to the tissue is a function of (i) the amount of currentpassing through heating element 46, (ii) the length, shape, and/or sizeof heating element 46, (iii) the resistive properties of heating element46, (iv) the gauge of heating element 46, and (v) the use of coolingfluid to control temperature. All of these factors can be variedindividually or in combination to provide the desired level of heat.Power supply 20 associated with heating element 46 may he battery based.Catheter 14 can be sterilized and may be disposable.

[0109] Referring now to FIG. 7, a thermal sensor 48 may be positioned inan interior location of catheter 14. In another embodiment, thermalsensor 48 is positioned on an exterior surface of catheter 14. A thermalsensor can be used to control the delivery of energy to thermal energydelivery device 18. A potting material can be used to fix the positionof thermal sensor 48 and provide a larger area from which to average themeasured temperature. Thermal sensor 48 is of conventional design,including but not limited to a thermistor; T type thermocouple with acopper constant an junction; J type, E type, and K type thermocouples;fiber optics; resistive wires; IR detectors; and the like. Optionally,there may be a lumen 42 for the thermal sensor connection.

[0110] As illustrated in FIG. 8, sheath 40 may be used to coverresistive heating element 46. A plurality of resistive heating elements46 can be used (FIG. 9) in a catheter of the invention.

[0111] Referring now to the embodiment shown in FIG. 10, thermal energydelivery device 18 comprises one or more resistive heating elements 46coupled to a resistive heating energy source. Resistive heating elements46 are positioned along intradiscal section 16 at locations where theycontrollably deliver thermal energy to selected structures, includinggranulation tissue in a fissure 44 and the annulus surrounding thefissure. Resistive heating elements 46 can be segmented and multiplexedso that only certain resistive heating elements, or combinations ofresistive heating elements are activated at any one particular time.Thermal sensor 48 can be positioned between resistive heating elements46 and/or at an exterior or interior location of catheter 14. In theembodiment illustrated in FIG. 10, catheter 14 can be prepared with awound helical structure element 49 to increase flexibility and minimizekinking. However, other structures and geometries are suitable forcatheter 14, including but not limited to a substantially smooth surface(and specifically including the device using an internal guide mandrelas previously described). For example, a sheath can be provided over theheating element, and the guiding mandrel inside the coil can beencapsulated in silicone potting material. The tubing flexibility andthe silicone potting material prevent kinking. Additionally, sheath 40can be positioned around catheter 14 and also around resistive heatingelements 46 to afford a substantially smooth surface. Resistive heatingelement 46 can be at least partially covered by a thermally insulatingmaterial, for example, along one side of the catheter, to selectivelyheat disc tissue on the opposite side.

[0112] Referring now to FIGS. 11 and 12, an open or closed loop feedbacksystem 52 couples sensors 48 to energy source 20. As illustrated in FIG.10, thermal energy delivery device 18 is a resistive heating element 46.It will be appreciated that the embodiments illustrated in FIGS. 10 and11 are readily adaptable to other thermal energy delivery sources (e.g.,for radiofrequency energy, the resistive heating element is replacedwith insulated RF probe(s) and the energy source is an RF generator).

[0113] The temperature of the tissue or of element 46 (FIG. 10) ismonitored by sensors 48, and the output power of energy source 20adjusted accordingly. The physician can, if desired, override controlsystem 52. A microprocessor can be included and incorporated in theclosed or open loop system to switch power on and off, as well as tomodulate the power. The closed loop system utilizes a microprocessor toserve as a controller 54 which acts to monitor the temperature andadjust the power accordingly. Alternatives to the microprocessor are,for example, analog control circuitry and a logic controller.

[0114] With the use of sensors 48 and feedback control system 52, atissue adjacent to resistive heating elements 46 can be maintained at adesired temperature for a selected period of time without aberrant hightemperature fluctuations. Each resistive heating element 46 can beconnected to separate control and power supply resources, which generatean independent output for each resistive heating element 46. Forexample, a desired thermal output can be achieved by maintaining aselected energy at resistive heating elements 46 for a selected lengthof time.

[0115] When a resistive heating element 46 is used, current deliveredthrough resistive heating element 46 can be measured by current sensor56. Voltage can be measured by voltage sensor 58. Resistance and powerare then calculated at power calculation device 60. These values canthen be displayed at user interface and display 62. Signalsrepresentative of power and resistance values are received by acontroller 54.

[0116] A control signal is generated by controller 54 that is related tothe current and voltages. The control signal is used by power circuits66 to adjust the power output in an appropriate amount in order tomaintain the desired power delivered at respective resistive heatingelements 46.

[0117] In a similar manner, temperatures detected at sensors 48 providefeedback for maintaining a selected power. The actual temperatures aremeasured at temperature measurement device 68, and the temperatures aredisplayed at user interface and display 62. A control signal isgenerated by controller 54 that is related to the actually measuredtemperature and a desired temperature. The control signal is used bypower circuits 66 to adjust the power output in an appropriate amount inorder to maintain the desired temperature delivered at the respectivesensor 48. A multiplexer can be included to measure current, voltage,and temperature at the sensors 48, 56 and 58, so that appropriate energycan be delivered to resistive heating elements 46.

[0118] Controller 54 can be a digital or analog controller or a computerwith software. When controller 54 is a computer, it can include a CPUcoupled through a system bus. Included in this system can be a keyboard,a disc drive or other non-volatile memory system, a display, and otherperipherals, as are known in the art. Also coupled to the bus can be aprogram memory and a data memory.

[0119] User interface and display 62 includes operator controls and adisplay. Controller 54 can be coupled to imaging systems well known inthe art.

[0120] The output of current sensor 56 and voltage sensor 58 is used bycontroller 54 to maintain a selected power level at resistive heatingelements 46. A predetermined profile of power delivered can beincorporated in controller 54, and a preset amount of energy to bedelivered can also be profiled.

[0121] Circuitry, software, and feedback to controller 54 result inprocess control and in the maintenance of the selected power that isindependent of changes in voltage or current. Control can include (i)the selected power and (ii) the duty cycle (wattage and on-off times).These process variables are controlled and varied while maintaining thedesired delivery of power independent of changes in voltage or current,based on temperatures monitored at sensors 48.

[0122] In the embodiment shown, current sensor 56 and voltage sensor 58are connected to the input of an analog amplifier 70. Analog amplifier70 can be a conventional differential amplifier circuit for use withsensors 48, 56 and 58. The output of analog amplifier 70 is sequentiallyconnected by an analog multiplexer 72 to the input of A/D converter 74.The output of analog amplifier 70 is a voltage which represents therespective sensed parameters. Digitized amplifier output voltages aresupplied by A/D converter 74 to microprocessor 54. Microprocessor 54 maybe a type 68HCII available from Motorola. However, it will beappreciated that any suitable microprocessor or general purpose digitalor analog computer can be used to the parameters of temperature, voltageor current.

[0123] Microprocessor 54 sequentially receives and stores digitalrepresentations of temperature. Each digital value received bymicroprocessor 54 corresponds to different parameters.

[0124] Calculated power and temperature values can be indicated on userinterface and display 62. Alternatively, or in addition to the numericalindication of power, calculated power values can be compared bymicroprocessor 54 with power limits. When the values exceedpredetermined power or temperature values, a warning can be given onuser interface and display 62, and additionally, the delivery ofelectromagnetic energy can be reduced, modified or interrupted. Acontrol signal from microprocessor 54 can modify the power levelsupplied by energy source 20.

[0125] In preferred embodiment of the invention, the materials that makeup the various parts of an apparatus of the invention have the followingcharacteristics: Tensile Strength Geometry (height, in % ConductivityResistivity Melt width, and/or dia.) Component MPa Elongationcal/cm²/cm/sec/° C. nΩ * m temp. ° C. in mm Mandrel 600-2000 5-100 N/AN/A N/A height 0.2-2.3 width 0.05-0.5 Heating Element 300 min 20 (min.).025-0.2 500-1500* N/A  0.5-0.5 dia. Conductor wire N/A N/A   2-1.0 150max.* N/A  0.1-0.5 dia. Plastic sheath N/A 25 (min.) N/A N/A 80*0.05-0.2 thickness (min.)

[0126] Another preferred characteristic is that the minimum ratio ofheating element resistivity to conductor wire resistivity is 6:1; thepreferred minimum ratio of guiding mandrel height to guiding mandrelwidth is 2:1. Tensile strength and % elongation can be measuredaccording to ASTME8 (tension test of metallic materials). Conductivityand resistivity can be determined by procedures to be found in ASTM Vol.2.03 for electrothermal properties.

[0127] A particularly preferred embodiment of a catheter of theinvention can be prepared using a covering sheath of polyimide with anoutside diameter of 1 mm and a wall thickness of 0.05 mm. Such a sheathprovides a significant fraction of the stiffness and torsional strengthappropriate for the catheter. Internal to the polyimide sheath and inthe intradiscal section of the catheter is a heating coil of insulatednickel/chromium wire that has an outside diameter that matches theinterior diameter of the polyimide sheath. This heating coil providesboth heat and additional stiffness to the assembly. Also internal to thepolyimide sheath on each side of the coil (longitudinally) is a 0.1mm-walled, 304 stainless-steel, metallic band whose outer diametermatches the inner diameter of the sheath, the distal band having ahemispherical end that exits the end of the polyimide sheath and createsa blunt tip 29 at the end of the catheter. These bands provide enhancedradio-opacity for fluoroscopic visualization, as well as some of thestiffness of the assembled apparatus. Proximal to the proximal metallicband and internal to the sheath is an additional polyimide tube 47 thatincreases the stiffness of the catheter in the region that transitionsfrom the intradiscal section containing the coil to the rigid proximalsection. Proximal to the second polyimide tube and internal to thesheath is a 304 stainless steel (fully hard) hypodermic tube with anoutside diameter matching the inside diameter of the polyimide sheathand a wall thickness of 0.1 mm. This combination provides the rigidityneeded for a physician to advance the distal portion of the deviceinside a nucleus pulposus and provides tactile force feedback from thetip to the physician.

[0128] In some embodiments, inside the bands, coil, hypodermic tube, andboth the polyimide sheath and internal polyimide tube is a guidingmandrel that extends from a proximal handle to tip. In one embodiment,this mandrel is 0.15 mm by 0.5 mm and formed from 304 stainless steel.In another embodiment, it is a 0.3 mm diameter 304 stainless steel wire,with the distal 2.5 cm flattened to 0.2 mm by 0.5 mm.

[0129] Inside the center of the heating coil is a T-type thermocouplepotted with cyanoacrylate adhesive into a polyimide sheath and locatedalongside the mandrel. The thermocouple wire travels through the coiland hypodermic tube to the handle at the proximal end of the apparatus.Two copper conductor wires (36 gauge-insulated with polyimide) aresoldered to the heating coil and pass through the hypodermic tube andhandle to the proximal handle's electrical connector, which allows apower supply and feedback controls to be connected to electricalelements in the catheter. One embodiment has the handle fitted with a1-3 meter cable extension ending in an electrical connector to eliminatethe need for a connector in the handle. This design reduces weight (fromconnector elements) on the proximal end and increases the physician'stactile feedback during device manipulation.

[0130] The entire inside of the catheter in one embodiment isencapsulated with a silicone material which removes air (which wouldinsulate the heat created by the heating coil) and helps support thepolyimide sheath to prevent collapse (i.e., increases stiffness).Instead of the silicone, another embodiment uses an epoxy which remainsflexible after curing. Strain relief is provided between the catheterbody and the handle with an elastomeric boot. The distal end of thecatheter is pre-bent 15-30° off the longitudinal axis of the catheter atabout 5-10 mm from the distal tip.

[0131] The catheter in one embodiment carries visible markings 38 on thehypodermic tube (with the markings being visible through the polyimidesheath) to indicate distance of insertion of the catheter into anintroducer and/or distance that the distal end of the catheter extendsout of the introducer into a disc. The catheter is also marked bothvisually and with tactile relief on its handle to indicate the directionof bending of the pre-bent tip and biased stiffness.

[0132] The guidable apparatus described herein can be used in any of anumber of methods to treat annular fissures. Specific methods that canbe carried out with an apparatus of the invention will now be described.

[0133] Discs with fissures can be treated non-destructively with orwithout the removal of nucleus tissue other than limited desiccation ofthe nucleus pulposus which reduces its water content. Fissures can alsobe ameliorated by shrinking the collagen component of the surroundingannulus to bring the sides closer to their normal position. Thermalshrinkage of collagen also facilitates ingrowth of collagen whichincreases annular stiffness. Fissures can also be repaired with sealantssuch as a filler (non-adhesive material that blocks the opening) and/orbonding material (adhesives or cements) which help seal the tear. Thefissure can also be treated with global heating of the disc. Most of theheat will be directed toward the fissure, but the remainder of the discwill also receive some heat.

[0134] In some methods of the invention, bonding materials such ascollagen, albumin, and a mixture of fibrinogen and thrombin aredelivered to the fissure. Collagen from a variety of sources can be used(e.g., bovine extracted collagen from Semex Medical, Frazer Pa., orhuman recombinant collagen from Collagen Corp., Palo Alto, Calif.). Thecollagen is injected dissolved or as a fine slurry, after which it isgradually thickens (or may be heated) in the fissure, where the injectedcollagen provides a matrix for collagen disposition by the body.

[0135] A variety of different materials can also be delivered to thedisc, such as, for example, to the fissure, including but not limited toelectrolyte solutions (i.e. normal saline), contrast media (e.g., Conraymeglumine iothalamate), pharmaceutical agents (such as the steroidmethylprednisolone sodium succinate available from Pharmacia & Upjohn.Kalamazoo, Mich., and nonsteroidal anti-inflammatory drugs),chemonucleolytic enzyme (e.g., chymopapain), hydrogel (such as disclosedin U.S. Pat. No. 4,478,822), osteoinductive substances (e.g., BMP, seeU.S. Pat. No. 5,364,839), chondrocyte inductive substance (e.g.,TGF-.beta.) and the like. The materials are delivered via the catheterand/or introducer to the disc. Preferably, however, when precisionplacement of the material (as in a fissure) is necessary or desired, thedelivery method uses the apparatus described above, especially whendelivery to the posterior, posterior lateral, or posterior medial regionof the disc is desired. The materials may be administered simultaneouslyor sequentially, such as beginning with an electrolytic solution (whichhelps the physician view the pathology) and following with products toseal a fissure.

[0136] The materials are delivered in an amount sufficient to decreasethe extent of the fissure at least partially, preferably to fill thefissure completely. The delivered material can be fixed in position withan adhesive, with a hydrogel that is liquid at room temperature gels atbody temperature, with naturally occurring processes (such asinteraction of fibrinogen and thrombin) within the disc, or by heatingthe disc as described in more detail below.

[0137] To seal a fissure, a combination of thrombin and fibrinogen isinjected at the fissure, after which it coagulates and forms a seal overthe fissure. A kit with appropriate syringes and other equipment isavailable from Micromedics, Inc., Eagan, Minn. Frozen fibrinogensolution is thawed in its plastic bag and then dispensed to a small medcup. Thrombin is reconstituted with sterile water in the “slow gel”concentration (100 units/ml) for tissue bonding. For example, 100 ml isadded to a vial containing 10,000 units. Thrombin solution is withdrawnfrom the vial and dispensed to a second med cup. The two syringes arefilled equally, one with each solution. Then the syringe tips are eachtwisted into an applicator that mixes the solutions before passing themto an administration tube. The syringes are fitted into the dual syringeholder and the plunger link, which helps the practitioner administerequal amounts of thrombin and fibrinogen. Then the practitioner connectsthe administration tube to the proximal end of the inventive catheter,depresses the plungers and dispenses the sealant solution to thefissure. The thrombin and fibrinogen react and form a natural seal overthe fissure.

[0138] Chymopapain can be injected through the subject catheter,particularly near a herniation of the disc. Chymopapain splits sidechains off proteoglycan molecules, thereby decreasing their ability tohold water and their volume. The disc gradually loses water anddecreases in size. A typical dose is 0.75 to 1.0 ml (2000 pKat/ml).

[0139] In some embodiments, thermal energy is delivered to a selectedsection of the disc in an amount that does not create a destructivelesion to the disc, other than at most a change in the water content ofthe nucleus pulposus. In one embodiment there is no removal and/orvaporization of disc material positioned adjacent to an energy deliverydevice positioned in a nucleus pulposus. Sufficient thermal energy isdelivered to the disc to change its biochemical and/or biomechanicalproperties without structural degradation of tissue.

[0140] Thermal energy is used to, e.g., cauterize granulation tissuewhich is pain sensitive and forms in a long-standing tear or fissure,and/or ablate granulation tissue. Additionally or alternatively, thermalenergy is used to seal at least a part of the fissure. To do that, thedisc material adjacent to the fissure is typically heated to atemperature in the range of 45-70° C. which is sufficient to shrink andweld collagen. In one method, tissue is heated to a temperature of atleast 50° C. for times of approximately one, two, three minutes, orlonger, as needed to shrink the tissue back into place.

[0141] Delivery of thermal energy to the nucleus pulposus removes somewater and permits the nucleus pulposus to shrink. This reduces a“pushing out” effect that may have contributed to the fissure. Reducingthe pressure in the disc and repairing the fissure may help stabilizethe spine and reduce pain.

[0142] Fissures can also be ameliorated by shrinking the collagencomponent of the annulus to bring the sides of the fissure closertogether in their normal position, creating a smaller annularcircumference. Electromagnetic energy can be applied to heat and shrinkthe collagen component of the annulus fibrosus. This reduces theredundancy in the disc roll that is created in a degenerative disc. Thisalso reduces the “pushing out” effect that created a containedherniation. The tightening and stiffening of the annulus fibrosus helpsthe disc function more normally. Tightening the annulus fibrosus canhelp stabilize the spine and relieve pain. Careful application ofelectromagnetic energy locally increases the stiffness of the disc inappropriate locations without overheating and harming other parts of thedisc.

[0143] Electromagnetic energy also can be applied to shrink collagen inthe nucleus pulposus. Delivery of electromagnetic energy to the nucleuspulposus removes some water and permits the nucleus pulposus towithdraw. This also can reduce the “pushing out” effect. Shrinking thedisc, such as, for example, by shrinking of the nucleus pulposus byreducing water content, and/or tightening up the annulus fibrosus wallcan create a rejuvenation of the disc. Reducing the pressure in the discand tightening the annulus fibrosus can produce a favorablebiomechanical effect.

[0144] Global heating of the disc also can be used to cauterize thegranulation tissue and seal the fissure. In this embodiment of themethod, the heating element is positioned away from the annulus butenergy radiates to the annulus to raise the temperature of the tissuearound the fissure. This global heating method can help seal a largearea or multiple fissures simultaneously.

[0145] The energy delivery device can be configured to deliversufficient energy to the intervertebral disc to provide a denervation ofa nerve at a selected site of the intervertebral disc. For example,degenerative intervertebral discs with fissures can be treated bydenervating selected nerves that are, for example, imbedded in theinterior wall of the annulus fibrosus or that are located outside of theinterior wall including those on the surface of the wall.Electromagnetic energy can be used to cauterize granulation tissue whichis a pain sensitive area and formed in the annulus fibrosus wall.Sufficient thermal energy also can be delivered to selectively denervatenociceptors in and adjacent to, for example, a fissure.

[0146] All publications and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication or patent application was specificallyand individually indicated to be incorporated by reference.

[0147] The foregoing description of preferred embodiments of theinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many modifications andvariations will be apparent to practitioners skilled in this art. It isintended that the scope of the invention be defined by the followingclaims and their equivalents.

[0148] A number of embodiments have been described. Nevertheless, itwill be understood that various modifications may be made. Accordingly,other embodiments are within the scope of the following claims.

What is claimed is:
 1. A method of treating an intervertebral disc, themethod comprising: inserting an introducer into an intervertebral dischaving a contained disc herniation; inserting a catheter through theintroducer and into the intervertebral disc; advancing a distal regionof the catheter through a nucleus pulposus of the intervertebral disc toan inner wall of an annulus fibrosus by blunt dissection; deliveringradiofrequency (“RF”) energy to material of the intervertebral discusing an electrode disposed at the distal region of the catheter; andremoving the material with the delivered RF energy, wherein removingmaterial with the delivered RF energy reduces pressure in theintervertebral disc to treat the disc herniation.
 2. The method ofclaims 1 wherein removing the material comprises removing water.
 3. Themethod of claim 1 wherein removing the material with the delivered RFenergy comprises ablating the material.
 4. The method of claim 1 or 3wherein removing the material comprises removing disc tissue.
 5. Themethod of claim 1, 2, or 3 wherein advancing the distal region of thecatheter through the nucleus pulposus comprises advancing the distalregion along a curved path.
 6. The method of claim 1, 2, or 3 whereinthe introducer comprises a needle and inserting the introducer comprisesinserting the needle.
 7. The method of claim 6 further comprisinginserting the needle and a trocar.
 8. The method of claim 6 whereininserting a needle comprises inserting a 17-gauge needle.
 9. The methodof claim 8 further comprising inserting the needle and a trocar.
 10. Themethod of claim 1, 2, or 3 further comprising providing the catheterwith a total length between 5 and 24 inches.
 11. The method of claim 1,2, or 3 wherein advancing the distal region of the catheter comprisesadvancing the catheter so that a maximum distance the catheter extendsfrom the introducer is no greater than one and one-half times thecircumference of the nucleus pulposus.
 12. The method of claim 1, 2, or3 wherein delivering RF energy comprises delivering RF energy from abipolar electrode configuration.
 13. The method of claim 1, 2, or 3further comprising twisting the catheter after inserting the catheterinto the intervertebral disc.
 14. The method of claim 13 whereinadvancing the distal region of the catheter through the nucleus pulposuscomprises advancing the distal region along a curved path.
 15. Themethod of claim 1, 2, or 3 further comprising heating the material to atemperature in a range of 45-70 degrees C. with the delivered RF energy.16. The method of claims 1, 2, or 3 further comprising heating thematerial to a temperature of 55 degrees C. with the delivered RF energy.17. The method of claims 1, 2, or 3 further comprising heating thematerial to a temperature of 65 degrees C. with the delivered RF energy.18. The method of claim 1, 2, or 3 further comprising denervating atleast a portion of the intervertebral disc with the delivered RF energy.19. The method of claim 1, 2, or 3 wherein advancing the distal regioncomprises advancing the electrode beyond the introducer.
 20. The methodof claim 1, 2, or 3 wherein delivering RF energy comprises delivering RFenergy to the inner wall of the annulus fibrosus.
 21. The method ofclaim 1, 2, or 3 wherein delivering RF energy comprises delivering RFenergy while the catheter is positioned at a location adjacent the innerwall of the annulus fibrosus.
 22. The method of claim 1, 2, or 3 whereindelivering RF energy comprises delivering RF energy to multiplelocations in the intervertebral disc using at least the electrode. 23.The method of claim 22 wherein delivering RF energy to multiplelocations comprises delivering RF energy to the multiple locationssimultaneously.
 24. The method of claim 22 wherein delivering RF energyto multiple locations comprises: delivering RF energy to at least afirst of the multiple locations using the electrode; and delivering RFenergy to at least a second of the multiple locations using a secondelectrode.
 25. The method of claim 22 wherein delivering RF energy tomultiple locations comprises delivering RF energy to the multiplelocations serially.
 26. The method of claim 22 wherein delivering RFenergy to multiple locations comprises delivering RF energy to themultiple locations using the electrode.
 27. The method of claim 1, 2, or3 further comprising advancing the catheter along the inner wall of theannulus fibrosus.
 28. The method of claim 1 wherein advancing the distalregion of the catheter comprises conforming the catheter sufficiently tothe inner wall of the annulus fibrosus to contact multiple locations onthe inner wall.